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Prevent FP contractions to FMA in index/.../content.hpp to avoid numerical instability in rtree #1453

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tinko92 merged 1 commit into from
Apr 14, 2026
+18 −0
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Prevent FP contractions to FMA in index/.../content.hpp to avoid numerical instability in rtree #1453

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18 changes: 18 additions & 0 deletions include/boost/geometry/index/detail/algorithms/content.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,8 @@
#ifndef BOOST_GEOMETRY_INDEX_DETAIL_ALGORITHMS_CONTENT_HPP
#define BOOST_GEOMETRY_INDEX_DETAIL_ALGORITHMS_CONTENT_HPP

#include <boost/config.hpp>

#include <boost/geometry/core/access.hpp>
#include <boost/geometry/core/coordinate_dimension.hpp>
#include <boost/geometry/core/coordinate_type.hpp>
Expand All @@ -26,6 +28,18 @@

namespace boost { namespace geometry { namespace index { namespace detail {

#if defined(BOOST_GCC)
// The following pragmas set fp-contract=off for GCC, to prevent surprising and
// subtle numerical behaviour changes as a result of cross-statement/function
// FMA contractions which can result in e.g. content(b1) - content(b2) != 0
// (or < 0) for content(b1) == content(b2) (or >=), due to the fp-contract=fast
// default from at least GCC 4.4 to present GCC 15.2. This avoids Github issue
// #1452. Safe to remove after numerically robust handling of degenerate cases
// is ensured at all index::detail::content(box) call sites.
#pragma GCC push_options
#pragma GCC optimize ("fp-contract=off")
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#endif

template <typename Indexable>
struct default_content_result
{
Expand Down Expand Up @@ -98,6 +112,10 @@ typename default_content_result<Indexable>::type content(Indexable const& b)
>::apply(b);
}

#if defined(BOOST_GCC)
#pragma GCC pop_options
#endif

}}}} // namespace boost::geometry::index::detail

#endif // BOOST_GEOMETRY_INDEX_DETAIL_ALGORITHMS_CONTENT_HPP
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